I have a 87 300E with 140,000 miles. When the fuel gauge hits about 1/2 it will occasionally go nuts and quickly flip back and forth from empty to full. This happens as on occasion as the fuel level drops to empty. Other than this erratic behavior the gauge reads just fine. I think it's either a ground or sending unit issue. Any advice and can anyone tell me how to access the sending unit?

Thanks,

Jim

 

if you get a PM answer to this from someone, could you pass it on to me too, I have the same issue with mine, started about the same mileage, now at about 220K though

 

I have an 89 that does the same thing I would also be interested in the cause.

 

I am not sure if this will help but here a suggestion.

My problem is the temp gauge, it flipped up and down in random with no relation to coolant temperature. It turned out that a loose connector/wire in the instrument panel...

 

Thanks for the tip. I suspect it is either a loose connection, bad ground or dirty sending unit. I might tackle it this weekend. If I do I'll report back.

Jim

 

I was able to fix my fuel gauge. I have no idea if this will work for others. But if you are interested, I pulled the sending unit from the tank and sprayed some carb cleaner into the sending unit tube and then rotated the sending unit up and down so the float would slide back and forth. This seems to have solved the problem. Access to the sending unit is very easy. On my 300E the tank is located in the trunk right behind the rear seat. The sending unit is right in the center of the tank at the top. It is held in with a large nut. Remove the electrical connection and then loosen the nut. The sending unit will pull right out. If you perform this operation, be very careful about spilling any gas and the gas fumes. There is a fair amount of gas in the sending unit tube depending upon how much is in the tank. The sending unit takes a while to drain down given the very small hole in the bottom. Good luck.